1. Field of the Invention
This invention generally relates to laser eye surgery, and in particular, provides methods, devices, and systems for selectively ablating corneal tissue to improve the vision of patients having corneal irregularities.
Laser eye surgery systems and methods are now used to correct defects in vision using a technique known as ablative photodecomposition. In general, these techniques selectively expose the cornea to laser radiation so as to selectively remove and resculpt the cornea and achieve a desired change in shape of the cornea to treat an optical defect.
Laser eye surgery is now being used to treat a variety of vision defects, including myopia (nearsightedness), hyperopia (farsightedness), and symmetrical cylindrical astigmatisms. To achieve these results, known laser eye surgery systems make use of a variety of mechanisms to selectively expose the corneal tissue to the ablative laser energy so as to change the optical characteristics of the eye uniformly throughout the optically used portion of the cornea. Often times, the desired change in shape is effected by selectively removing corneal tissue according to a spherical ablation profile (for example, for treatment of myopia and hyperopia). Cylindrical astigmatism is often treated by selectively removing corneal tissue according to a cylindrical profile, in which the cylinder extends laterally across the optical axis of the eye.
Many patients suffer from optical defects which are not easily treated using known spherical or cylindrical ablation techniques. It has been proposed to treat patients suffering from nonsymmetrical or other types of astigmatism by defining a custom ablation profile. Ophthalmic measurement techniques which may be capable of generating highly accurate topographic information on a particular cornea are now being developed. Unfortunately, integrating these topographic measurements together with new ablation algorithms may take years. In the meantime, patients having irregular corneal defects which significantly limit their vision are in need of treatment today.
In light of the above, it would be desirable to provide improved laser eye surgery devices, systems, and methods. It would be beneficial if these improvements allowed the treatment of irregular corneal defects, particularly if these benefits were available and safe for use in the near-term.
2. Description of the Background Art
The following patents and patent applications may be relevant to the present invention: U.S. Pat. No. 5,683,379, issued Nov. 4, 1997, for xe2x80x9cApparatus for Modifying the Surface of the Eye Through Large Beam Laser Polishing and Method of Controlling the Apparatusxe2x80x9d; U.S. Pat. No. 4,724,522, issued Feb. 9, 1988, for xe2x80x9cMethod and Apparatus for Modification of Corneal Refractive Propertiesxe2x80x9d; U.S. Pat. No. 5,098,426, issued Mar. 24, 1992, for xe2x80x9cMethod and Apparatus for Precision Laser Surgeryxe2x80x9d; U.S. Pat. No. 5,290,272, issued Mar. 1, 1994, for xe2x80x9cMethod for the Joining of Ocular Tissues Using Laser Lightxe2x80x9d; U.S. Pat. No. 5,314,422, issued May 24, 1994, for xe2x80x9cEquipment for the Correction of Presbyopia by Remodelling the Corneal Surface by Means of Photo-Ablationxe2x80x9d; U.S. Pat. No. 5,391,165, issued Feb. 21, 1995, for xe2x80x9cSystem for Scanning a Surgical Laser Beamxe2x80x9d; U.S. Pat. No. 5,439,462, issued Aug. 8, 1995, for xe2x80x9cApparatus for Removing Cataractous Materialxe2x80x9d; U.S. Pat. No. 5,549,596, issued Aug. 27, 1996, for xe2x80x9cSelective Laser Targeting of Pigmented Ocular Cellsxe2x80x9d; U.S. Pat. No. 5,549,597, issued Aug. 27, 1996, for xe2x80x9cIn Situ Astigmatism Axis Alignmentxe2x80x9d; U.S. Pat. No. 5,556,395, issued Sep. 17, 1996, for xe2x80x9cMethod and System for Laser Treatment of Refractive Error Using an Offset Image of a Rotatable Maskxe2x80x9d; U.S. Pat. No. 5,634,919, issued Jun. 3, 1997, for xe2x80x9cCorrection of Strabismus by Laser-Sculpting of the Corneaxe2x80x9d; U.S. Pat. No. 5,637,109, issued Jun. 10, 1997, for xe2x80x9cApparatus for Operation on a Cornea Using Laser-Beamxe2x80x9d; PCT International Application No. PCT/EP95/01287, filed Apr. 7, 1995, for xe2x80x9cMethod and Apparatus for Providing Precise Location of Points on the Eyexe2x80x9d; European Patent Application No. 94303256.5, filed May 5, 1994, for xe2x80x9cMethod and System for Laser Treatment of Refractive Errors Using Offset Imagingxe2x80x9d; and U.S. patent application Ser. No. 09/274,499, filed Mar. 23, 1999, for xe2x80x9cMultiple Beam Laser Sculpting System and Methodxe2x80x9d. The full disclosure of these references is hereby incorporated by reference.
The present invention provides improved laser eye surgery devices, systems, and methods. The invention provides near-term customized ablation capabilities for treatment of corneal irregularities by ablating standard refractive therapy profiles at a position which is offset from the pupillary center. These treatment profiles may, when centered on the eye, be suitable for treatment of standard refractive errors such as myopia, hyperopia, and symmetrical cylindrical astigmatism. By selectively offsetting one or more of these ablation profiles at selected points across the corneal surface, the laser system can reduce refractive errors resulting from corneal irregularities such as irregular astigmatism, corneal steepening in one quadrant, asymmetrical astigmatism, irregularities inadvertently produced by a prior refractive treatment (such as radial keratotomy incisions, a decentered ablation, asymmetric warpage as a result of corneal transplants, penetrating keratoplasty, or the like), granular dystrophy, diffuse, bilateral keratoconus, or the like.
In a first aspect, the invention provides a method for treating an eye of a patient. The eye has a cornea and a pupil, the pupil having a center. The method comprises aligning a laser delivery system with the pupil of the eye. A treatment center on the cornea is designated so that the treatment center is offset laterally (in the X and/or Y direction) from the center of the pupil. A region of the cornea is ablated by directing laser energy according to a therapy profile centered at the treatment center, which may be at some distance from the pupillary center.
The therapy may further comprise selecting the therapy profile from a library including a myopic treatment profile, a hyperopic treatment profile, and a cylindrical treatment profile. These treatment profiles may be scaled for both size and power, and still further therapy profiles may be included in the library. A more complete library may include myopic ablations which are spherical, cylindrical, and/or elliptical in shape; hyperopic ablations which are spherical, cylindrical, and/or provide smooth transition zones; and optionally including therapeutic ablations such as phototherapeutic keratectomy slits and/or phototherapeutic keratectomy circles of variable sizes and having variable transition zones.
Corneal irregularities will often benefit from combinations of two or more therapy profiles centered at different treatment centers on the cornea. By providing a variety of different treatment profiles which can be scaled and selectively offset from each other, often at least partially overlapping on the corneal surface, a wide variety of customized contoured ablations may be effected without having to generate individual customized ablation algorithms to effect the desired overall treatment profile.
The particular profile or profiles applied to a patient""s eye will often be identified or planned using a map of the cornea. Elevation maps, such as those which might be produced using wavefront technology now under development, are particularly beneficial for selecting, scaling, and offsetting the therapy profiles over the corneal surface to mitigate the corneal irregularity. Advantageously, it is not necessary to (although it is possible to) link these developmental topography systems to the ablation system to generate customized therapies. Instead, a system operator may select individual ablation size, shape, location, and power based on a topography map, so as to plan the total combined treatment, optionally simulating the effect of the proposed ablation before it is implemented. In fact, while elevation map data results are preferred due to their accuracy and location, depth, and size of irregular corneal features, tangential and/or axial maps may be used independently and advantageously combined to supply the desired information.
In another aspect, the invention provides a system for treating an eye of a patient. The eye has a cornea and pupil with a center. The system comprises a laser producing a laser beam capable of ablating the cornea. Delivery optics are coupled to the laser. Alignment optics are aligned with the delivery optics for maintaining alignment between the laser and the pupil of the eye. An input for designating at least one treatment center is coupled to the delivery optics. The treatment center is offset laterally from the center of the pupil while the pupil of the eye is aligned with the alignment optics.
In a standard symmetrical ablation, alignment optics are aligned with the delivery optics so that the delivered laser beam is coincident and concentric with the alignment reticle. The patient""s pupil is generally aligned to the reticle of the alignment optics. If a treatment is desired wherein the treatment beam is not to be centered on the pupil, the operator can specify how far and in what direction the beam is to be displaced from the alignment center. Typically, a controller will direct the optics to deflect the beam laterally so as to effect a treatment profile centered about the designated treatment center. The treatment profile will often be produced by directing numerous individual laser pulses over varying overlapping regions of the cornea. The controller and delivery optics may make use of small spot scanning techniques, large area ablation techniques with variable blocking of the laser energy, and/or overlapping intermediate sized spots which are laterally deflected using mirrors, lenses, or the like. The controller may effect the treatment profiles by moving scanning mechanisms, selecting apertures, varying iris or slot sizes, often according to a treatment table or position calculation algorithm. Regardless, the controller will preferably have and/or make use of a tangible data storage medium with a library of alternative refractive therapies which may be selected and/or scaled individually or in combinations. The library will typically include profiles suitable for treatment of myopia, hyperopia, and cylindrical astigmatism when centered on the optical axis of the eye. By offsetting one or more of these therapies, a wide variety of corneal irregularities may be treated.